1. Field of the Invention
This invention relates to a hotmelt adhesive, to its production and use and to moldings produced with the hotmelt adhesive.
2. Discussion of Related Art
Hotmelt adhesives are adhesives solid at room temperature which are temporarily melted to perform their adhesive function. They are based essentially on polyamides, polyolefins or polyesters and mixtures thereof. By incorporation of additives, they can be further optimized for the particular applications envisaged.
Thus, a hotmelt adhesive for bonding non-pretreated polyethylene and copper in accordance with DE-OS 35 04 804 consists essentially of the following compatible components:
a) polyamides based on dimerized fatty acids, aliphatic amines and modifying additives, PA1 b) copolymers of ethylene, the inner anhydride of an ethylenically unsaturated dicarboxylic acid and optionally (meth)acrylates and/or vinyl esters and PA1 c) other auxiliaries such as, for example, compatibility promoters and tackifiers. PA1 a) a polyamide based on one or more dimeric fatty acids, PA1 b) an ethylene/acrylic acid/butyl acrylate terpolymer containing free carboxyl groups and optionally PA1 c) an acrylic rubber preferably in the form of a copolymer of ethyl acrylate, butyl acrylate, methoxyethyl acrylate and ethoxyethyl acrylate. PA1 a) 5 to 30% by weight of a polyamide based on dimerized fatty acids with an amine value of 0.5 to 15, PA1 b) 50 to 90% by weight of an ethylene/vinyl acetate copolymer which is hydrolyzed according to the statement of invention, but not in the comparative tests, PA1 c) 5 to 30% by weight of a block copolymer of styrene/butadiene/styrene or styrene/isoprene/styrene and optionally PA1 d) tackifiers, such as terpene, terpene/phenol and alkylphenol resin. PA1 a) copolymer of ethylene and .alpha.,.beta.-unsaturated carboxylic acid and/or an alkyl ester thereof and vinyl acetate where the copolymer does not contain any alkyl ester units, PA1 b) copolymer of ethylene and unsaturated carboxylic acid. PA1 a) polyamide based on dimerized fatty acid, PA1 b) acidic ethylene copolymers with an acid value of around 3 to 80 and PA1 c) a tackifier, more particularly a polyketone resin. PA1 a) at least 50% by weight of at least one polyamide based on dimerized fatty acid, PA1 b) 5 to 20% by weight of at least one ethylene copolymer selected from the group consisting of ethylene/vinyl acetate, ethylene/acrylate, said acrylate being derived from an alcohol containing 1 to 18 carbon atoms, and ethylene/methacrylate, said methacrylate being derived from an alcohol containing 1 to 18 carbon atoms, PA1 c) 2 to 10% by weight of at least one copolymer of styrene with one or more members selected from the group consisting of ethylene, isoprene and butylene, PA1 d) 5 to 25% by weight of at least one plasticizer, PA1 e) 0 to 10% by weight of at least one tackifying resin from the group consisting of polycyclopentadiene, polyterpene, liquid hydrocarbon resin and PA1 f) 0 to 15% by weight of at least one copolymer of monomers selected from the group consisting of ethylene, propylene, butylene and maleic anhydride. PA1 up to 55 mole-% and, more particularly, 35 to 49.5 mole-% of dimerized fatty acid, PA1 up to 15 mole-% and, more particularly, 0.5 to 15 mole-% of at least one monomeric fatty acid containing 12 to 22 carbon atoms and PA1 up to 35 mole-% and, more particularly, 2 to 35 mole-% of at least one polyether diamine corresponding to the following general formula: EQU H.sub.2 N--R.sub.1 --O--(R.sub.2 O).sub.x --R.sub.3 --NH.sub.2(I) PA1 x is a number of 8 to 80, mainly from 8 to 40, PA1 R.sub.1 and R.sub.3 may be the same or different and represent aliphatic and/or cycloaliphatic hydrocarbon radicals preferably containing 2 to 8 carbon atoms, PA1 R.sub.2 is an optionally branched aliphatic hydrocarbon radical containing 1 to 6 carbon atoms, PA1 up to 48 mole-% and, more particularly, 15 to 48 mole-% of at least one aliphatic and/or cycloaliphatic diamine containing 2 to 40 carbon atoms, up to two thirds of the dimerized fatty acids being replaceable by aliphatic dicarboxylic acids containing 4 to 12 carbon atoms. PA1 up to 55 mole-% and, more particularly, 35 to 49.5 mole-% of dimerized fatty acid, PA1 up to 15 mole-% and, more particularly, 0.5 to 15 mole-% of at least one monomeric fatty acid containing 12 to 22 carbon atoms and PA1 up to 55 mole-% and, more particularly, 45 to 55
Although ethylene or propylene can be bonded with high strength values by compositions such as these without any need for the otherwise usual pretreatment and although the low-temperature properties are still remarkably good at -20.degree. C. and lower, the known hotmelt adhesives have the following disadvantage: their softening points are too high, for example for the processing of shrunk articles. Softening points of &lt;130.degree. C. are generally required for this application.
EP-A1-0 040 926 also describes a hotmelt adhesive for bonding untreated polyethylene. This known hotmelt adhesive contains
The document in question does not provide any information on the viscosity and softening point of the hotmelt adhesive so that it may well be that the products described are unsuitable for certain applications, for example for the processing of shrunk articles. For adhesion to non-pretreated polyethylene, it is important to bear in mind that, in many cases, not only high strengths, but also a balanced ratio of adhesion to substrate surface/inner cohesion is required so that, besides high strength values, a cohesive fracture pattern is also obtained in peel tests. None of this is mentioned in EP-A1-0 040 926.
U.S. Pat. No. 4,552,819 describes a hotmelt adhesive for coating shrinkable moldings of polyethylene for the electrical industry, more particularly the cable industry, which contains the following components:
This composition has the disadvantage that adhesion to non-pretreated polyethylene cannot be obtained. In addition, the softening points are too high.
Finally, EP-A1-0 079 178 describes a hotmelt adhesive for bonding non-pretreated polyethylene which has the following composition:
The composition may also contain thermoplastics, such as polyethylene for example. Compositions such as these have the disadvantage that they lack sufficient resistance to chemicals.
DE-OS 23 47 799 describes heat-resilient moldings of crosslinked polyethylene with at least one layer of a hotmelt adhesive of the following composition:
This hotmelt adhesive has the disadvantage of inadequate adhesion to non-pretreated polyethylene.